1. Field of the Invention
The present invention relates to a chuck assembly for a wafer transfer apparatus used during the processes of manufacturing semiconductor devices, and more particularly to a chuck assembly for an automatic wafer transfer apparatus equipped with contamination prevention means.
2. Background of the Related Art
As shown in FIG. 1, the prior art automatic wafer transfer apparatus uses a chuck assembly 1 to remove a group of wafers 10 from a quartz boat 30 that has been unloaded from a process chamber and deliver them into a wafer cassette 40, and to remove the group of wafers from the wafer cassette and deliver them into the quartz boat.
The chuck assembly 1 comprises at least a pair of wafer retainers 20a and 20b for accommodating the group of wafers 10. Each of the wafer retainers 20a and 20b comprises a wafer guide 21a or 21b and a guide supporter 22a or 22b attached to the wafer guide 21a or 21b. The wafer guides 21a and 21b face each other.
As shown in FIG. 2, a plurality of slots 23 for accommodating the group of wafers 10 are formed at regularly spaced intervals in the facing sides of wafer guides 21a and 21b. Similar slots (not shown) are formed inside quartz boat 30, as is well known in the art. Also, as shown in FIG. 3, a plurality of slots 41 are formed at regularly spaced intervals inside the wafer cassette 40 to thereafter transport a group of wafers 10 to the subsequent process step.
Referring again to FIG. 1, the chuck assembly 1 for an automatic wafer transfer apparatus operates as follows to move wafers 10 to and from quartz boat 30 and wafer cassette 40. First, chuck assembly 1 moves downwardly to a quartz boat 30 (or wafer cassette 40) to retrieve wafers 10 therein. Next, the chuck assembly 1 holding the wafers 10 moves upwardly and horizontally into position over an empty wafer cassette 40 or quartz boat 30. And then, the chuck assembly 1 moves downwardly to load the wafers 10 into the wafer cassette 40 or quartz boat 30 without scratching the wafers 10.
However, in this conventional art, when wafers are retrieved from a quartz boat, quartz particles are produced and deposited inside the slots of the quartz boat due to contact between the wafers and the quartz boat. These particles are disturbed and become airborne when the next wafers are loaded into the quartz boat and these next wafers become contaminated with the particles. In addition, the particles are carried up into the slots 23 in the wafer guide and may become lodged therein.